Virossi are a mysterious WATER archetype consisting of Aqua monsters with an unique trait, they're a specialized parasite lifeform that force their hosts to bend to their will, their strategy consists of taking control of their opponent's monster and taking advantage of this, by applying effects that reveal their opponent's strategies and cards that check those anticipated cards.

They cooperate with each other or enhance themselves individually to increase their size in order to prey on bigger foes, they can take control of opponent's monsters but most of them can't make good use of their abilities, they ultimately rely on their opponent's to make the bigger splash, since the deck isn't fast enough and is strictly opponent reliant, their own capacity varies and can be rendered performing poorly if they can't make the best use of their mind controlling abilities.

They're strictly monster reliant, and need to perform their effects successfully in order to perform at an acceptable pace, they also can't just take over any monster, they need to enhance their DEF in order to be in a good range to take over monsters... Despite of that, we're dealing with a deck that specializes entirely on taking the opponent's monster and probing their information, if that is not scary, then I don't know what to think...

Virossi VeinWATER****[Aqua/Union/Effect]You can Normal Summon this card in Defense Position. This card gains DEF equal to its Level x200. During each Standby Phase, increase this card's level by 1. During Either player's turn you can target 1 Non-''Virossi'' Monster on the field with an ATK equal to or lower than this card's DEF; Equip this card to that target as an Union card OR, Special Summon this card in Defense Position. A monster equipped with this card shifts control to this card's owner, it cannot activate it's effects and it gains 400 ATK. (A monster can only be equipped with 1 Union Monster at a time, if this card would be Destroyed, you can Banish the equipped monster and Return this card to the Hand instead)ATK/0 DEF/1000

Virossi NerverWATER****[Aqua/Union/Effect]You can Normal Summon this card in Defense Position. ''Virossi'' Monsters gain DEF equal to its Level x100. During each Standby Phase, increase the levels of all ''Virossi'' Monsters by 1. During Either player's turn you can target 1 Non-''Virossi'' Monster on the field with an ATK equal to or lower than this card's DEF; Equip this card to that target as an Union card OR, Special Summon this card in Defense Position. A monster equipped with this card shifts control to this card's owner, it cannot attack. (A monster can only be equipped with 1 Union Monster at a time, if this card would be Destroyed, you can Banish the equipped monster and Return this card to the Hand instead)ATK/0 DEF/1400

Virossi GlobuleWATER****[Aqua/Union/Effect]You can Normal Summon this card in Defense Position. This card gains DEF equal to its Level x200. During each Standby Phase, increase this card's level by 1. During Either player's turn you can target 1 Non-''Virossi'' Monster on the field with an ATK equal to or lower than this card's DEF; Equip this card to that target as an Union card OR, Special Summon this card in Defense Position, and if you do, Reveal your opponent's hand and all Set cards they control. A monster equipped with this card shifts control to this card's owner, its effects are negated and it loses 500 ATK and DEF. (A monster can only be equipped with 1 Union Monster at a time, if this card would be Destroyed, you can Banish the equipped monster and Return this card to the Hand instead)ATK/0 DEF/1200

Virossi BacterianWATER***[Aqua/Union/Effect]You can Normal Summon this card in Defense Position. This card gains DEF equal to its Level x500. During Either player's turn you can target 1 Non-''Virossi'' Monster on the field with an ATK equal to or lower than this card's DEF; Equip this card to that target as an Union card OR, Special Summon this card in Defense Position. A monster equipped with this card shifts control to this card's owner. If this card or the equipped Monster is destroyed: Special Summon 2 ''Virossi'' Monsters with the same name from your Deck with a DEF equal to or lower than the ATK of the equipped Monster.(A monster can only be equipped with 1 Union Monster at a time)ATK/0 DEF/0

Virossi VitamiWATER***[Aqua/Union/Effect]You can Normal Summon this card in Defense Position. ''Virossi'' Monsters gain DEF equal to its Level x300. During each Standby Phase, increase the levels of all ''Virossi'' Monsters by 1. During Either player's turn you can target 1 Non-''Virossi'' Monster on the field with an ATK equal to or lower than this card's DEF; Equip this card to that target as an Union card OR, Special Summon this card in Defense Position. A monster equipped with this card shifts control to this card's owner. If this card or the equipped Monster is destroyed: Special Summon 1 or more ''Virossi'' Monsters with the same name from your Graveyard.(A monster can only be equipped with 1 Union Monster at a time)ATK/0 DEF/600

Virossi Exo TalamusWATER++++[Fiend/Xyz/Effect]2 Level 4 opponent's Monsters you currently controlWhile this card has Xyz materials, ''Virossi'' Cards you control cannot be Destroyed by card effects. During either player's turn, you can detach 2 Xyz Materials from this card: if there was any monster(s) among them, take control of all Monsters your opponent controls with the same Type and Attribute as the detached Monster(s). If this card is in the Graveyard, you can pay 1000 LP; Special Summon this card by attaching 1 monster you control equipped with a ''Virossi'' equip card to this card as Xyz Material and returning that Equip card to the Hand, and if you do, reveal all Set cards your opponent controls.ATK/2700 DEF/2500

Virossi FibrousWATER****[Fiend/Xyz/Effect]2 Level 4 ''Virossi'' Monsters(Original level)When this card is Xyz Summoned, reveal all cards in your opponent's Hand and all Set cards they control, cards and effects cannot be activated in response to this effect. Any Monster this card Destroys by battle is attached to a ''Virossi'' Xyz Monster you control as Xyz material. When a Monster effect is activated, you can Detach 1 Xyz Material from cards you control; if the detached monster's Type is the same as that Monster's, negate it's activation and if you do, take control of it. When this card leaves the field; Special Summon up to 2 Monsters that were attached to it as Xyz Materials.ATK/2500 DEF/500

Virossi MatrixWATER+++++[Psychic/Xyz/Effect]3 level 5 MonstersYou can also Xyz Summon this card by using an opponent's Monster you control and a ''Virossi'' Xyz Monster you control as Xyz materials(Xyz Materials Attached to Xyz Monsters also become Xyz materials to this card). This card is unaffected by Spell/Trap effects. While this card has Xyz materials, your opponent must play with their Hand revealed. Once per turn, you can Detach 1 Xyz Material from this card; Special Summon 1 ''Virossi'' Monster from your Deck or Graveyard, it's DEF becomes 3000. When this card leaves the field, add 2 ''Virossi'' cards from your Deck to your Hand.ATK/2000 DEF/3000

Virossi Spread Spell Card/NormalAdd 1 ''Virossi'' Monster from your Deck to your Hand, then Destroy all non-''Virossi'' Monsters you control. You can Normal Summon ''Virossi'' Monsters in addition to your Normal Summon/Set for each of those.

Virossi ResearchSpell Card/NormalTarget any number of Monsters equipped with ''Virossi'' Equip cards; Destroy them and Draw 1 card for each of those targets. While this card is in the Graveyard, except the turn it was sent there, when a Monster shifts control to your field, you can banish this card; Draw 1 card.

Virossi DischargeSpell Card/Quick-playIf you control a Monster equipped with a ''Virossi'' Equip card, Declare 1 card name; your opponent must reveal all cards in their hand and all Set cards they control, if there's any card(s) of the declared name among them, Destroy them, and if you do, Special Summon ''Virossi'' Monsters from your Graveyard for each card destroyed this way. Otherwise Banish all ''Virossi'' Equip cards you control and return all Monsters you control to their original owners.

Virus IncubatorSpell Card/ContinuousDuring each End Phase, place 1 Vein Counter on this card. ''Virossi'' Monsters you control gain 100 DEF for each Vein Counter on the field. ''Virossi'' cards you control cannot be destroyed by card effects, except ''Virossi Incubator''. During either player's turn, you can remove Vein Counters from this card, activate one of the following effects:* 1: Place 1 ''Virossi'' Card from your Graveyard on top of your Deck.* 2: Add 1 ''Virossi'' Monster from your Deck to your hand.* 3: Immediately after this effect resolves, Equip 1 ''Virossi'' Monster you control to an opponent's monster as an Union card.

Viral LeakTrap card/NormalTarget 1 ''Virossi'' Union Monster you control; Equip it to an opponent's monster as an Union Card. If this card is destroyed by a card effect, you can add 2 ''Virossi'' cards from your Deck to your Hand.

Virossi CardiiaWATER****[Fairy/Tuner/Effect]If your opponent controls a Monster while you control no monsters, you can Special Summon this card. When this card is Special Summoned: you can add 1 ''Virossi'', ''Aggro Device'' or ''Slicer'' Spell/Trap card from your Deck to your Hand. Once per turn, if your opponent controls 2 Monsters, you can pay 1000 LP; Your opponent switchs control of one of their monsters, that monster's Type, Attribute, Level and Name become the same as this card's, You can only use this effect of ''Virossi Cardiia'' once per turn. You cannot Xyz Summon Monsters, except ''Virossi'' Xyz Monsters.

Virossi Mind RegulatorSpell Card/ContinuousYou can Normal Summon 1 ''Virossi'' or ''Slicer'' Monster in addition to your Normal Summon/Set(You can only gain this effect once per turn). During your turn, if you control a ''Slicer'' Monster, you can shuffle 1 card from your Hand in your Deck; Special Summon 1 ''Virossi'' Monster from your Deck or Graveyard, that card cannot be used as an Xyz Material, except for the Xyz summon of a ''Virossi'' Monster. You can only use each effect of ''Virossi Mind Regulator'' once per turn.